Water adsorption characteristics at Pt step-edge decorated Cu(211) surfaces

Investigations into catalyst surfaces show that low-coordination sites, such as steps and defects, can strongly influence adsorption and reaction pathways. This study examines water interaction with Cu(211) step edges and how decorating these steps with Pt modifies adsorption behavior on Pt/Cu(211) surfaces. Techniques employed include infrared reflection absorption spectroscopy (IRRAS) and temperature-programmed desorption (TPD) to link surface structure and composition with water adsorption characteristics.

Key findings:

• On pristine Cu(211), step edges exhibit high chemical activity toward water, binding water molecules more strongly and promoting partial dissociation to form hydroxyl (OH) groups. Partial dissociation of the first water layer at Cu step sites and the formation of adsorbed OH strongly influence the adsorption strength of molecular water at the step edges; hydrogen bonding to pre-formed OH groups can stabilize surface water, enabling the formation of chain-like water-OH structures.
• Decoration of Cu step edges with Pt fundamentally alters this behavior. On fully Pt-decorated step sites, water adsorbs molecularly rather than dissociating to OH, and the formation of stable OH–water chains is suppressed.
• Pt decoration also disrupts the long-range organization of water multilayers, facilitating crystalline ice formation under the same conditions where it does not occur on the pure Cu(211) surface. This indicates that Pt at the step edges reshapes the water adlayer structure at the atomic scale.

These results demonstrate that the atomic-scale structure of a surface, particularly step edges, decisively governs water interaction with Cu-based catalysts. By controlling surface structure and bimetallic composition, it may be possible to tailor surfaces that effectively activate reactants while resisting poisoning, enhancing catalytic efficiency and durability in aqueous and electrochemical environments.

Project summary: Sarp Kaya, Associate Professor, Department of Chemistry, Koç University, Istanbul, Türkiye.

Paper Reference: Mohammadpour, A. and Kaya, S. (2024) ‘Probing water adsorption characteristics of Pt step-edge decorated Cu(211) surface.’ Surface Science. Elsevier BV, 748, October, p. 122537. DOI: 10.1016/j.susc.2024.122537.

Hiden product: HAL 201 RC.